Boris Balats

Photometry and IR-metry in Parameters Control of Plasma Etching at Atmospheric Pressure Thinning of silicon wafers prior to dicing into chips and packaging is a complicated technological process. The method of Plasma Etching at Atmospheric Pressure (PEAP) significantly simplifies the technological process of thinning due to a possibility to exclude several auxiliary operations [1,2]. PEAP is a cyclic scanning of the wafer surface by a plasma flow of a given composition. A double-jet plasmatrone is a the source of the plasma at atmospheric pressure. Argon is a plasma forming gas. A component is necessary for the chemical reaction, e.g. CF4, can be inserted into the plasma flow. The wafer is placed on a non-contact rotated holder, the work side facing the plasma generator. The wafer is processed by scanning of its surface periodically while the holder passes through the plasma flow. The equipment and technology problems that may be solved by using the optoelectronic devices are clear from the purpose and conditions of the PEAP process. Controlling the plasma flow configuration. The laminar regime of outflow of the plasma generating flows leads to a high jet sensitivity to the focus conditions and to the convection environment effects. Observance of the jet geometry is one of the pre-conditions of precise parameter maintenance of the plasma generator [3]. The developed plasma-monitoring device was consists of an optic receiver, an electronic unit and a magnetic deflection unit, fig.1 After processing the optic image, the magnetic deflection unit receives an individual control signal for every jet. The control signal is formed in several tens of nanoseconds. Signals are produced with a 200 msec period due to the inertia of the plasma jet. Process control and graphic mapping of information are provided in real time. The device enables to maintain the plasma jet position in the measurement plane with an error of no more than 0.1 mm. This precision is quite satisfactory to achieve the stable performance of the generator. Measurement of the temperature of the processed wafer. The technology of manufacturing integral circuits highly depends on the temperature of the wafers and the uniformity of their heating. Overheating leads to accelerate of aging of the units in spite of the absence of a visible damage. Non-uniform heating is responsible for the deformation of the wafers that can persist due to the cooling conditions. Conclusion Above-shown methods of photo- and IR-metry are reliable tools that provide the reproducibility and high quality of the process of the plasma etching at atmospheric pressure. The used software enables to create a feedback for controlling of the working parameters of the equipment. For example, less than 2% thickness non-uniformity was obtained after 350 mm layer smoothing for 200 mm diameter wafer. Reference O.V. Siniaguine, B.M. Balats, I.P. Bagriy, Silicon wafers plasma treatment at atmospheric pressure, Electronic Industry, No. 6, (1994), P.p. 27 - 30. Russia B.M. Balats, The details of plasma jet silicon wafers treatment at atmospheric pressure, Abstracts of technical symposium papers, SEMI CIS executive mission and exhibit. Zelenograd, Russia, (1998), P.p. 46-48. O.U. Budnik, V.E. Dolgirev, I.M. Tokmoulin, Plasma stream monitoring software, NPO "ROTOR", Equipment for high technology, Cherkassy, V. 1, (1990), P.p. 72-78. USSR. Gusev V.E., Karabutov A.A., Lazernaya optoakustika, M., Nauka, (1991), P. 304. USSR.